Java 如果非零，Joda-Time DateFormatter 显示毫秒
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Joda-Time DateFormatter to display milliseconds if nonzero
提问by Mike
Using Joda-Time, I want to display a list of dates that may or may not have milliseconds on them. If a certain entry has milliseconds, then it should be displayed like yyyy MM dd HH:mm:ss.SSS. If it doesn't have the millis, I need it displayed as yyyy MM dd HH:mm:ss.
使用Joda-Time，我想显示一个日期列表，这些日期可能有也可能没有毫秒。如果某个条目有毫秒，那么它应该显示为yyyy MM dd HH:mm:ss.SSS。如果它没有毫秒，我需要将其显示为yyyy MM dd HH:mm:ss.
I suppose the general question is: Is there a way to describe an optional format string parameter?
我想一般的问题是：有没有办法描述一个可选的格式字符串参数？
(I'd like to avoid refactoring all of the places that I use formatters since this is a large code base.)
（我想避免重构我使用格式化程序的所有地方，因为这是一个大型代码库。）
采纳答案by MetroidFan2002
As far as I know, there's no optional patterns. However, I think you may be overthinking your problem.
据我所知，没有可选的模式。但是，我认为您可能过度考虑了您的问题。
// Sample variable name - you'd probably name this better.
public static DateTimeFormat LONG_FORMATTER = DateTimeFormatter.forPattern("yyyy MM dd HH:mm:ss.SSS");
// Note that this could easily take a DateTime directly if that's what you've got.
// Hint hint non-null valid date hint hint.
public static String formatAndChopEmptyMilliseconds(final Date nonNullValidDate) {
final String formattedString = LONG_FORMATTER.print(new DateTime(nonNullValidDate));
return formattedString.endsWith(".000") ? formattedString.substring(0, formattedString.length() - 4) : formattedString;
}
The length may not be exactly right for the substring (untested code), but you get the idea.
长度可能不完全适合子字符串（未经测试的代码），但您明白了。
